But for their help, we the program in time．
A. can not finish
B. will not finish
C. had not finished
D. could not have finished
网友回答
A. can not finish
B. will not finish
C. had not finished
(答案→)D. could not have finished
解析：考查虚拟语气。But for“要不是......”，相当于if虚拟条件句，与过去事实相反，主句用would/should/could have done。句意“要不是他们的帮助，我们不可能及时完成计划。”故选D。